Centre National de la Recherche Scientifique Unité Mixte de Recherche 6061, Institut de Génétique et Développement de Rennes, Université de Rennes 1, 35000 Rennes, France.
Mol Biol Cell. 2010 Jun 15;21(12):2078-86. doi: 10.1091/mbc.e09-11-0926. Epub 2010 Apr 21.
Notch receptors mediate short-range signaling controlling many developmental decisions in metazoans. Activation of Notch requires the ubiquitin-dependent endocytosis of its ligand Delta. How ligand endocytosis in signal-sending cells regulates receptor activation in juxtaposed signal-receiving cells remains largely unknown. We show here that a pool of Delta localizes at the basolateral membrane of signal-sending sensory organ precursor cells in the dorsal thorax neuroepithelium of Drosophila and that Delta is endocytosed in a Neuralized-dependent manner from this basolateral membrane. This basolateral pool of Delta is segregated from Notch that accumulates apically. Using a compartimentalized antibody uptake assay, we show that murine Delta-like 1 is similarly internalized by mNeuralized2 from the basolateral membrane of polarized Madin-Darby canine kidney cells and that internalized ligands are transcytosed to the apical plasma membrane where mNotch1 accumulates. Thus, endocytosis of Delta by Neuralized relocalizes Delta from the basolateral to the apical membrane domain. We speculate that this Neuralized-dependent transcytosis regulates the signaling activity of Delta by relocalizing Delta from a membrane domain where it cannot interact with Notch to another membrane domain where it can bind and activate Notch.
Notch 受体介导短程信号，控制后生动物的许多发育决定。Notch 的激活需要其配体 Delta 的泛素依赖性内吞作用。配体在内源信号细胞中的内吞作用如何调节毗邻的信号接收细胞中的受体激活，在很大程度上仍然未知。我们在这里表明，在果蝇背部胸部神经上皮的信号发送感觉器官前体细胞中，Delta 定位于基底外侧膜，并且 Delta 以 Neuralized 依赖性的方式从该基底外侧膜内化。这种基底外侧的 Delta 池与 Notch 隔开， Notch 积累在顶端。使用分隔的抗体摄取测定法，我们表明，鼠类 Delta-like 1 也可通过极化的 Madin-Darby 犬肾细胞中的 mNeuralized2 从基底外侧膜内化，并且内化的配体被转胞吞到顶端质膜，其中 mNotch1 积累。因此，Neuralized 介导的 Delta 内吞作用将 Delta 从基底外侧膜重新定位到顶端膜域。我们推测，这种 Neuralized 依赖性的转胞吞作用通过将 Delta 从不能与 Notch 相互作用的膜域重新定位到可以与 Notch 结合并激活 Notch 的另一个膜域，从而调节 Delta 的信号活性。
